A liquid crystal panel including an active matrix substrate is used for products such as flat panel televisions, tablet devices, and smartphones. In applications of large-size panels represented by flat panel televisions, there has been a demand for higher drive frequency for realization of three dimensional display and a moving image with higher quality, a higher pixel count such as 4K resolution (4K2K) or the like, and a larger screen size. On the other hand, in applications of small to medium-size panels represented by tablet devices and smartphones, there has been an increasing demand for a pixel size with higher definition (fine pixel size) and a narrower frame by virtue of a circuit incorporating technology. For responding to those demands, in the active matrix substrate, a TFT element having higher mobility and higher integration, and a signal line having lower resistance are required. In this regard, an interest has been expressed in forming a channel of the TFT with an oxide semiconductor instead of amorphous silicon, which has been hitherto typically used. In particular, a TFT using a transparent amorphous oxide semiconductor (TAOS) has recently attracted attention as a device achieving both a higher carrier mobility and uniformity in characteristics.